Constant on time internal combustion engine ignition system



y 0, 1966 B. H. SHORT 3,250,867

CONSTANT ON TIME INTERNAL COMBUSTION ENGINE IGNITION SYSTEM Filed April 2'7, 1964 3 Sheets-Sheet 1 INVENTOR.

Brooks A. 6720)? BY C fR W May 10, 1966 B. H. SHORT 3,250,867

CONSTANT ON TIME INTERNAL COMBUSTION ENGINE IGNITION SYSTEM Filed April 27, 1964 3 Sheets-Sheet 2 INVENTOR.

Brooks A. 6720)) BY 0 I R IM 2913 flTTORA EY May 10, 1966 B. H. SHORT 3,250,367

CONSTANT ON TIME INTERNAL COMBUSTION ENGINE IGNITION SYSTEM Filed April 27, 1964 3 Sheets$heet 5 S/ezu Speed O bereh'on 5/01. [4? 610550 B ROTATION 51m. .40 610550 r I e c i 0 f! .90 15.4" 50m names/A L ems/:0

High Speed Operah'on BKR. Z5 CLOSED E 6' ROTATION BKR. 5o anew-14 F 0 E i i i I I I l 00 a .90 a

P cem mveze 50TH BREAKERS CLOSED INVENTOR.

Brooke 1'2. 6720;? BY

HM .47 TORIVEY United States Patent 3 250,867 CONSTANT ON TIME INTERNAL COMBUSTION ENGINE IGNITION SYSTEM Brooks H. Short, Anderson, Ind., assignor to General -Mot'ors Corporation, Detroit, Mich., a corporation of Delaware Filed Apr. 27, 1964, Ser. No. 362,750 4 Claims. (Cl. 20027) This invent-ion relates to an ignition system for an internal combustion engine and more particularly to an ignition system which maintains a substantially constant on time for the primary winding current regardless of includes a cam that has alternate lobes and flat surfaces.

In this type of system, the time that the breaker contacts 'are closed which is the time that current is supplied to the primary winding varies with engine speed with the result that power is wasted at low speeds since the system must be designed to provide optimum ignition performance at the highest speed expected.

It accordingly is one of the objects of this invention to provide an ignition system which has a substantially constant on time for primary winding current at varying engine speeds.

Another object of this invention is to provide an ignition system wherein the on time for primary winding current is controlled by two timing devices which are so arranged as to provide a substantially constant on time for primary winding current regardless of engine speed.

Another object of this invention is to provide an ignition system where a pair of switching means are connected in the primary winding circuit and wherein the closure of the switching means is arranged such that a substantially constant time of energization of the primary winding from the power source is established at various engine speeds.

Still another object of this invention is to provide an ignition system wherein primary winding current is controlled by two sets of breaker contacts whose operation is synchronized to provide a substantially constant time of energization for the primary winding of the ignition system at varying engine speeds. I n A further object of this invention is to provide an ignition system which is controlled by two speed responsive devices which are so connected that a substantially constant time of energization for the primary winding of the ignition coil can be obtained at varying engine speeds. 7

Another object of this invention is to provide a distributor which is capable of controlling primary winding current in an ignition system and which is capable 3,250,867 Patented May 10, 1966 ice will be apparent from the following description, reference being had to the accompanying drawings wherein preferred embodiments of the present invention are clearly shown.

In the drawings:

FIGURE 1 is a schematic circuit diagram of an ignition system made in accordance with this invention.

FIGURE 2 is a sectional view of a distributor which has breaker contacts for controlling the system shown in FIGURE 1.

FIGURE 3 is a sectional view taken along line 3-3 of FIGURE 2.

FIGURE 4 is a sectional view taken along line 44 of FIGURE 2.

FIGURE 5 is a sectional view taken along line 55 of FIGURE 2.

FIGURE 6 is a sectional view taken along line 6-6' of FIGURE 2.

FIGURE 7 is a' chart illustrating the closure of the two sets of breaker contacts of the ignition system at a slow speed condition of the engine.

FIGURE 8 is a chart similar to FIGURE 7 but illustrating the closure .of the breaker contacts with a high speed condition of the engine.

winding current.

Further objects and advantages of the present invention reference numerals 28 and 30.

Referring now to the drawings and more particularly to FIGURE 1, an ignition system is illustrated which includes a conventional ignition coil designated by reference numeral 10. This ignition coil 10 has a primaryv winding 12 and a secondary winding 14. The secondary winding 14 feeds a rotor contact 16 which swings past the inserts or electrodes 18 in the distributor cap 20. The electrodes or inserts 18 are connected with the spark plugs 22 on an engine 23 all of which is well known to those skilled in the art.

One side of the primary winding 12 is connected with an ignition switch 24, the opposite side of the ignition switch being connected to a source of direct current 26 which is shown as a battery. The opposite side of the primary winding 12 can be connected to ground through two sets of breaker contacts designated respectively by It will be appreciated that primary winding current cannot flow through the primary 12 until both sets of breaker contacts 28 and 30 are closed.

Referring now more particularly to FIGURES 2, 4 and 6, a distributor is illustrated which controls the opening and closing of the breaker contacts 28 and 30. The breaker contacts 28 are illustrated in FIGURE 6 and it is seen that these contacts can be opened by a breaker cam 32 which engages a rubbing block 34 on the lever 36 that carries one of the breaker contacts 28. The lever 36 is pivotally mounted as is conventional practice and forms a part of a contact set 39 which is mounted on a timing plate 40.

It can be seen from FIGURE 2 that the cam 32 is connected with a weight base 42. The weight base 42 pivotally supports fly weights 44 which cooperate with the cam plate 46 in a conventional manner. The cam plate 46 is connected with a breaker cam 50 and with a weight base 52. The weigh-t base 52 pivotally supports fly weights 54 which cooperate with the cam plate 56. The cam plate 56 is directly driven by a shaft ,58 journalled for rotation in the base 60.

The cam 50 as seen in'FIGURE 4 operates a breaker lever 62 by means of rubbing block 64. The breaker lever 62 carries one of the breaker contacts 30 and is pivotally supported in the usual manner and forms part of-a conventional contact set 66 which is secured to a timing plate 68. The timing plate 68 is mechanically connected to the timing plate 40 by the annular member 70 formed of insulating material. The timing plate 40 has a pin 72 which is connected with the movable part of a conventional vacuum unit 74 which is connected with the intake manifold of the engine. The vacuum unit 74 adjusts both timing plates 40 and 68 together because of their connection through part 70.

The distributor cap 20 has the usual center electrode 78 and the circumferentially spaced electrodes or inserts 18 which go to the spark plugs. The rotor contact 16 is carried by the conventional insulator rotor part 80 which is secured to the weight base 52 by screws as is well known to those skilled in the art.

The distributor illustrated in FIGURE 2 when in use on an engine 23 has its shaft 58 connected with the cam shaft of the engine in a manner well known to those skilled in the art. The vacuum unit 74 is connected with the intake manifold of the engine so that the timing plates 40 and 68 are adjusted in accordance with the vacuum in the intake manifold. The dotted lines in FIGURE 1 indicate the mechanical connection between the engine and the distributor.

The opening and closing of the breaker contacts 28 and 30 are depicted in FIGURE 7 for a slow speed condition of the engine. In FIGURE 7, the full lines indicate the angle of rotation over which the breaker contacts 30 are closed while the dotted lines indicate the angle of rotation over which the breaker contacts 28 are closed.

As the shaft 58 is rotatably driven, the fly weights 54 adjust the cam 50 relative to the shaft 58 to provide centrifugal advance for the ignition system. The breaker cam 32 is adjusted by the weight plate 42 and is driven by an extension of cam 50 through the cam plate 46 and the fiy weights 44. The cam 32 is therefore adjusted in accordance with the speed of rotation of the cam 50 and the fly Weights 44 will advance the cam 32 with respect to the cam St) in accordance with shaft speed.

The effect of this construction is depicted in FIGURE 7. Thus at point A on FIGURE 7, the breaker contacts 30 are closed. After rotation of earns 32 and 50 through an angle between points A and B, the breaker'contacts 28 close. It is seen that the primary winding 12 is not energized upon the initial closure of breaker contacts 30 at point A since at that time the breaker contacts 28 are open. At point B, both sets of breaker contacts 28 and 30 are closed and the primary winding 12 is now energized. The primary winding 12 will be energized until breaker contacts 30 open which occurs at point C. Thebreaker cams pass through an angle which is equal to the distance between points B and C in the FIGURE 7 chart when both sets of breaker contacts are closed and the primary winding 12 is therefore energized over an angle of rotation of the cams depicted betweenpoints B and C.

The centrifugal advance mechanism which includes fly weights 44 and cam plate 46 is arranged such that as the speed of rotation of the shaft increases, the breaker contacts 28 close earlier in the cycle. This higher speed condition is depicted in FIGURE 8 Where it is seen that the breaker contacts 30 close at point D while the breaker contacts 28 close at point E. The breaker contacts 30 open at point F while the breaker contacts 28 open at point G. The angular distance between points E and F which corresponds to the time when the primary winding 12 is energized, has been increased as compared to the FIGURE 7 situation and since the engine and the shaft 58 are now operating at a higher speed, the primary winding 12 of the ignition coil will be energized for substantially the same length of time at the low speed of FIG- URE 73nd at the high speed of FIGURE 8.

From the foregoing, it will be appreciated that the time that the primary winding 12 is energized from the source of direct current will be substantially constant regardless of engine speed since the centrifugal advance mechanism which includes the weights 44 and the cam plate 46 operates to vary the angle over which both sets of contacts are closed in response to engine speed.

While the embodiments of the present invention as herein disclosed, constitute a preferred form, it is to be understood that other formsmight be adopted.

What is claimed is as follows:

1. An ignition timing device comprising, a base, a shaft adapted to be driven by an engine rotatably supported by said base, first and second timing plates, said timing plates being connected together and adjustable relative to said shaft, a vacuum unit for adjusting said timing plates as a unit, first and second breaker contact apparatus supported respectively by said timing plates, a first centrifugal mechanism including a pair of fly weights connected with and driven by said shaft, a first breaker cam for operating said first breaker contact apparatus adjustable relative to said shaft by said first centrifugal mechanism, a second centrifugal mechanism including a pair of fly weights having an input member rigidly connected to said first breaker cam and having an output member rigidly connected to a second breaker cam, said second breaker cam operating said second breaker con-tact apparatus, said centrifugal advance mechanisms being so-constructed and arranged that the angle of rotation of said shaft over which both breaker contact apparatus is closed is increased in accordance with an increase in shaft speed.

2. An ignition timing device comprising, a base, .a shaft adapted to be driven by an engine rotatably supported by said base, first and second axially spaced breaker contact apparatus, a first centrifugal mechanism including a pair of fly weights having an input member rigidly connected to said shaft and an output member rigidly connected to a first breaker cam, said first breaker cam operating said first breaker contact apparatus, a second centrifugal mechanism includinga second pair of fly weights, said second centrifugal advance mechanism having an input member rigidly connected to said first breaker cam and having an output member connected to a second breaker cam, said second breaker cam operating said second breaker contact apparatus, said centrifugal mechanisms being so-constructed and arranged that the angle of rotation of said shaft over which both breaker contact apparatus is closed is increased as shaft speed increases.

3. An ignition timing device comprising, first and second breaker contact apparatus adapted to be connected in series with the primary winding of an ignition coil, first and second breaker cams, a rotatable shaft, a first centrifugal mechanism having an input member rigidly connected to said shaft and an output member rigidly connected with said first breaker cam, said first centrifugal mechanism being operative to adjust said first breaker cam angularly relative to said shaft as a function of shaft speed, a second centrifugal advance mechanism having an input member and an output member, said input member being rigidly connected to said first breaker cam whereby said input member is adjusted in the same direction as said first breaker cam and rotates at the same speed as said first breaker cam, said output member of said second centrifugal mechanism being connected to said second breaker cam whereby said second breaker cam is angularly adjusted relative to said shaft as a function of the speed of rotation of said first breaker cam, said centrifugal advance mechanisms being so-constructed and arranged that the angle of rotation of said shaft over which both breaker contact apparatus is closed is increased with increasing shaft speed.

4. An ignition timing device comprising, a base, a shaft adapted to be driven by an engine rotatably supported by said base, first and second breaker contact apparatus, first and second breaker cams for respectively operating said first and second breaker contact apparatus, a first centrifugal mechanism including fly Weight means having an input member driven by said shaft and having an output member which is adjusted relative to said shaft as a function of shaft speed, means connecting said output member of said first centrifugal mechanism with said first breaker cam, a second centrifugal mechanism including fly Weight means having an input member coupled to said first breaker cam and having an output member which is adjusted relative to said shaft as a function of the speed of rotation of said first breaker cam, and means connecting the output member of said second References Cited by the Examiner UNITED STATES PATENTS Re. 17,074 9/1928 Hunt 123-1171 1,438,002 12/ 1922 Varley 20031 1,859,308 5/1932 Mallory 200-22 2,306,549 l2/1942 Louis 20031 MARK NEWMAN, Primary Examiner.

centrifugal mechanism with said second breaker cam, 5 RICHARD WILKINSON, Examiner- 

1. AN IGNITION TIMING DEVICE COMPRISING, A BASE, A SHAFT ADAPTED TO BE DRIVEN BY AN ENGINE ROTATABLY SUPPORTED BY SAID BASE, FIRST AND SECOND TIMING PLATES, SAID TIMING PLATES BEING CONNECTED TOGETHER AND ADJUSTABLE RELATIVE TO SAID SHAFT, A VACUUM UNIT FOR ADJUSTING SAID TIMING PLATES AS A UNIT, FIRST AND SECOND BREAKER CONTACT APPARATUS SUPPORTED RESPECTIVELY BY SAID TIMING PLATES, A FIRST CENTRIFUGAL MECHANISM INCLUDING A PAIR OF FLY WEIGHTS CONNECTED WITH AND DRIVEN BY SAID SHAFT, A FIRST BREAKER CAM FOR OPERATING SAID FIRST BREAKER CONTACT APPARATUS ADJUSTABLE RELATIVE TO SAID SHAFT BY SAID FIRST CENTRIFUGAL MECHANISM, A SECOND CENTRIFUGAL MECHANISM INCLUDING A PAIR OF FLY WEIGHTS HAVING AN INPUT MEMBER RIGIDLY CONNECTED TO SAID FIRST BREAKER CAM AND HAVING AN OUTPUT MEMBER RIGIDLY CONNECTED TO A SECOND BREAKER CAM, SAID SECOND BREAKER CAM OPERATING SAID SECOND BREAKER CONTACT APPARATUS, SAID CENTRIFUGAL ADVANCE MECHANISMS BEING SO-CONSTRUCTED AND ARRANGED THAT THE ANGLE OF ROTATION OF SAID SHAFT OVER WHICH BOTH BREAKER CONTACT APPARATUS IS CLOSED IN INCREASED IN ACCORDANCE WITH AN INCREASE IN SHAFT SPEED. 